Wilhelm mtjshoff



W. MUSHOFP.

BLAGKBOARD.

Patented Mar. 30, 1897*.

(No Model.)

Mr/JJM PATENT rrrcn.

WILHELM MUSHOFF, OF BUER, GERMANY.

BLACKBOARD.

SPECIFICATION forming part of Letters Patent No. 579,767, dated. March 30, 189'?.

Application filed September 28, 1896. Serial No. 607,254. (No model.) Patented in Germany December 10, 1895. No, 87,272.

T0 all whom it may concern:

Be it known that I, WILHELM MUsHoFF, a subject of the German Emperor, residing at Buer, Germany, have invented ycertain new and useful Improvements in Blackboards, (for which I have obtained a patent in Germany, No. 87,272, dated December lO, 1895,) of which the following is a specilication.

My invention relates to a blackboard, and has for its object to provide a simple and cheap construction, so that the board can be readily adjusted at any desired height and is also capable of being turned horizontally, so as to present either side to view. Ihave illustrated such improved blackboard in the anneXed drawings, making a part of this specification, same parts being designa-ted by the same letters of reference in the several gures, and wherein Figure l shows a front elevation of the blackboard and supporting-frame, partly in section. Fig. 2 shows a section on the line x a; of Fig. 1. Fig. 3 shows a section on the line y y of Fig. l, and Eig. 4 shows the lower part of the blackboard when in position for being turned.

'The blackboard proper, T, is mounted in a frame R and held therein by the two vertical pinions z c. The blackboard thus framed is arranged in and carried by the upright frame S and held therein by means of cords e passed over pulleys o, provided at the top of the upright frame S. The free ends of these cords are weighted by counterweights e', as shown. The frame R, surrounding the blackboard, is equipped at its upper end with studs a, a', that are engaged in grooves provided in the uprights of frame S or in the space provided between the slats of the uprights, if same are formed in two pieces, as shown in the drawings. The horizontal motion of the blackboard is normally prevented by means of the weighted catches c c. These catches are pivoted to the lower part of frame R and will prevent the blackboard from turning on its pivots ,e z,as clearly shown in Eig. l. Within the hollow lower part of this frame R are also provided two bolts r and r', normally projecting beyondsaid frame and catching in the grooves providedv in the uprights of the frame S. Toward the center of the lower part of frame R these rods are formed into racks s and S, that are acted upon by a pinion CL2, mounted on the lower pivot z", which pivot is also provided with a handle h, as shown, so that it may be readily turned by hand. The bolts r and 1" are also equipped with projections n and n', protruding through openings provided in the lower part of the frame R, and when the bolts are withdrawn from the slots in the uprights these projections will move the Weighted catches o and n into the position shown in Fig. 4. In this posit-ion the blackboard may be moved up or down or turned in its own frame R at will. As soon as the blackboard is in the desired position the handle h is moved in the opposite direction. The weighted catches o and c will then again drop into their normalr positions and the bolts r and r will reenter into the grooves of the uprights, thus firmly holding the blackboard in the desired position.

Having now described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. In a blackboard, the combination of supportingestandardaa frame vertically movable upon said standards, a blackboard supported by said frame, counterweights carried by said standards and connected to said frame, retaining-bolts horizontally located at opposite sides of said frame and provided with rackteeth at their inner ends, and a pinion provided with an operating-handle and engaging the teeth on both of said bolts to simultaneously move said bolts in opposite directions to engage said standards and support the frame in its adjusted position, substantially as described.

2. Ina blackboard, the combination of supporting-standards, a vertically-sliding frame carried by said standards and having pivoted therein a blackboard, means to prevent the rotation of said blackboard upon its pivots, retaining means to hold the frame at its vertical adjustment, and projections from said retaining means adapted when retracted to engage and release the means which prevent the rotation of the blackboard, substantially as described.

3. Ina blackboard, the combination of supporting-standards, a vertically-sliding frame IOO carried by said standards and having pivoted said pvoted Catches when the bolts are moved therein a blackboard, eounterweighted pivotto retract the same,substantially as described. 1o

ed catches attached to said frame to prevent Signed at Dusseldorf, Germany, this 30th rotation oi' the blackboard, sliding bolts earday of July, 1896.

5 ried by said frame to retain the same at its XVILHELM MUSI'IOFF.

vertical adjustment by engagement With said Witnesses: standards, and projections extending from WVM. ESSENWEIN,

said bolts and adapted to engage and release ERNEST ANDR. 

